Wow you must have been really lucky, or have a white window frames, or both. The first was the factory install and the second I installed, both were BLACK plastic, both started cracking and shrinking in the corners from excessive heat, really don't think the shrinking plastic was from over tightening or an alignment issue...... Been in construction all my life, and am a Master Carpenter, so I realize how important proper torque and frame alignment are, plus I have also seen the effects of the Phoenix and West TX sun on plastics. Also it sets in the sun 365 days a year, no indoor or covered storage. So trust me when I say that it was caused by the SUN. Thank you for your input, you have been a HUGE help......